Rotating electrical machines such as motors and generators are used in many industrial fields. Especially, axial gap rotating electrical machines are flat in shape and are capable of delivering large torque; therefore, it is expected that they will be applied to motors used in hybrid automobiles and motors of the outdoor units of air conditioners.
For example, JP-A-2007-228790 (Patent Document 1) discloses a two-rotor/one-stator axial gap rotating electrical machine. This rotating electrical machine is formed by providing a stator having multiple magnetic poles, obtained by combining a core and a coil, around a rotating shaft; and placing a rotor having multiple permanent magnets on both sides of the stator with a predetermined air gap in the direction of the rotating shaft.
In this type of axial gap rotating electrical machine, it is important for the enhancement of efficiency to accurately control the distance of the air gap between the rotor and the stator.
For example, if the distance of the air gap between a rotor and a stator is larger than desired, the attractive force and repellent force between the stator and the rotor can become smaller than desired. This leads to the degraded performance of the rotating electrical machine. For this reason, it used to be required to maintain the high dimensional accuracy of the air gap when a rotating electrical machine is assembled.
In general, axial gap rotating electrical machines are so structured that parts comprising the axial gap rotating electrical machine are stacked along the direction of the axis of its rotating shaft. Therefore, the dimension errors of each component are accumulated and it used to be difficult to ensure an accurate air gap.
It is an object of the invention to provide an axial gap rotating electrical machine in which it is possible to accurately control the distance of the air gap between a rotor and a stator.